Air dynamometer having water injection spray nozzles

ABSTRACT

The range of operation of an air dynamometer used as a power absorption device in testing prime movers such as electric motors, gas turbines and internal combustion engines is improved by injecting a water spray into the air inlet of the air dynamometer so that the working fluid is a mixture of air and water.

United States Patent [1 1 McClure 51 Jan. 16, 1973 [54] 3 AIR DYNAMOMETER HAVING WATER INJECTION SPRAY NOZZLES [75] Inventor: John W. McClure, Charleston, S.C.

[73] Assignee: Arco Corporation, Charleston, S.C.

[22] Filed: June 1, 1971 [21] Appl. No.: 148,803

[52] US. Cl ..73/l34, 188/290 [51] Int. Cl. ..G0ll 3/20 [58] Field of Search ..239/425.5, 428, 77, 78; 73/134; 188/290, 296

[56] References Cited UNITED STATES PATENTS 3,138,328 6/1964 Glasby ..239/77 2,667,717 2/1954 Daugherty ..239/428 2,674,494 4/1954 Matteson et al ..239/78 3,135,466 6/1964 Reid ..239/77 2,537,800 1/1951 Stoeckly ..73/134 X 2,599,315 6/1952 Boyd et a1. ..73/134 Primary Examiner-Charles A. Ruehl AttorneyCharles M. Hogan and Irwin P. Garfinkle [5 7] ABSTRACT The range of operation of an air dynamometer used as a power absorption device in testing prime movers such as electric motors, gas turbines and internal combustion engines is improved by injecting a water spray into the air inlet of the air dynamometer so that the working fluid is a mixture of air and water.

5 Claims, 2 Drawing Figures PATENTEDJAN 16 ms v 400 500 600 MILLILITERS WATER PER MINUTE a Q T N NL .hx E 0 W w m A AIR DYNAMOMETER HAVING WATER INJECTION SPRAY-NOZZLES engines and others, it is desirable to load the output shaft with a known and measurable torque so that performance can be evaluated. These devices are generally referred to as dynamometei's arid they operate by absorbing the power of the prime mover under test. one such dynamometer, an air dynamometer, is a turbomachine consisting of an impeller designed to do work by moving air, 'much as in the same way as a propeller. The impeller is coupled to the output shaft of the prime mover arid is encased in a housing which permits air to enter through one orifice and exit through another.

The power absorbed by an air dynamometer is proportional to the product of the energy head and the mass flow rate of the air. The energy head is a function of the diameter of the rotating impeller and its speed. The mass flow rate is proportional to the product of the density of the air, its velocity, and the cross sectional area of the inlet orifice. It follows therefore that the passage of increased mass flow will require proportionately greater power by the prime mover. Increased mass flow may be achieved by increasing air density, the air velocity, and the cross sectional area of the inlet. In the disclosed invention I increase the density of the mass flow. Normally such increases occur due to varia-- tions in ambient conditions, and these are usually very small and oftentimesneglected. In the instant case I increase the fluid density by injecting water spray into the inlet of the dynamometer. The working 'fluid then becomes a mixture of water and air, the mixture ratio of which may be controlled, the minimum ratio being zero, and the maximum ratio being that which is compatible with the structural integrity of the rotating components.

Objects of the Invention It is a primary object of this invention to provide a relatively simple and effective means for increasing the range of the power absorption capability of an air dynamometer by injecting a water spray into the normal air inlet of an air dynamometer.

THE DRAWINGS FIG. 1 is illustrative of an embodiment of this invention; and

FIG. 2 is a curve showing the percentage increase in power absorption versus milliliters of water per minute injected into the air dynamometer inlet.

DESCRIPTION or THE INVENTION 'is supplied through opposed nozzles 22 and 24. The

fluids mixed in the chamber 18 pass through fluid inlet opening 26 in the housing 'wall and are acted upon by the impeller 10. The mixed fluids are then exhausted through a tangentially located fluid exit orifice 28.

The water spray introduced into the chamber18 through the nozzles 22 and 24 may be supplied from any controllable source. In the embodiment as reduced to practice the water was gravity fed from a tank 32, and the flow rate from the tank' was controlled by means of valves 34 and 36. The electric motor was supplied from a two-phase, l 18 volts, 60 cycle alternating current source 38.

The power absorbed by the illustrated dynamometer was determined by measuring the power (current, voltage, and phase angle) required by the motor 14. First, measurements were made of the amount of air flow through the impeller and the electrical power required to produce it. Water was then injected into the air inlet stream by means of the two nozzles 22 and 24 placed 180 apart. The amount of water injected was determined by measuring the changing level in the tank 32 over a known period of time. The increase in power required by the electric motor 14 was then measured and recorded. The tests were repeated for different amounts of water injection, keeping the speed of the impeller and the air flow constant. The results of the tests are plotted in FIG. 2, and are tabulated in the following table:

Measured Power Water Flow Air Only Air-water Air Flow Milli liters Watts Watts Increase SCFM per Minute Test 1 653 721 10.3 308 714 Test 2 663 694 4.67 308 319 Test 3 665 697 6.9 308 377 Test 4 7 680 3.61 308 277 Test 5 660 720 9.1 308 552 The test data indicates a requirement of approximately 700 milliliters per minute of water mixed in an air flow of 308 cubic feet per minute to yield a 10 percent=increase in the power absorbed. On a mass flow basis this amount of water (700 milliliters) represents about 7 percent of the total mass flow with 308 SCFM of air.

Summary of the Invention In summary, this invention produces an increased range of operation for an air dynamometer by injecting water vapor into the air flow of an air dynamometer. The results of tests conducted on such a dynamometer show that such water injection significantly increases the power absorption capability of existing turbomachine designs in a predictable manner.

Iclaim:

1. A dynamometer type power absorption device for use in testing the performance of a prime mover having a rotatable output, the combination comprising:

a rotatable impeller connectable to said output;

a housing for said impeller;

a fluid inlet in said housing and a fluid outlet in said housing;

means for admitting air to said inlet to provide a I flowing fluid mass through said housing;

and means for increasing the density of said fluid mass, said means comprising means at said inlet for injecting a water spray into said flowing fluid =mass, whereby the power absorption capability of said device is increased.

means for injecting said water spray comprises a nozzle connectable to a supply of water.

5. The invention as defined in claim 3 wherein said means for injecting said water spray comprises first and second opposed nozzles, each of said nozzles being connectable to a source of water.

l I I! i i (5/69) m m n QCERHHCATE @l MERHEMEEUN Patent No. 3,7l0,6l9 Dated January 16, 1973 Inventor), John W. McClure It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

L'ine reading "Assignee: Arco Corp. Charleston, S. C.

should read Assignee: Avco Corp., Charleston, S. C.

Signed arid sealed this 29th dag 9,1? Ma x 1 75 (SEAL) Attesc:

EDWARD M.F LETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner" of Patents 

1. A dynamometer type power absorption device for use in testing the performance of a prime mover having a rotatable output, the combination comprising: a rotatable impeller connectable to said output; a housing for said impeller; a fluid inlet in said housing and a fluid outlet in said housing; means for admitting air to said inlet to provide a flowing fluid mass through said housing; and means for increasing the density of said fluid mass, said means comprising means at said inlet for injecting a water spray into said flowing fluid mass, whereby the power absorption capability of said device is increased.
 2. The invention as defined in claim 1, and means for controlling the amount of water spray admitted at said inlet.
 3. The invention as defined in claim 1 wherein said fluid inlet includes a mixing chamber, said chamber having an air inlet, said means for injecting said water spray being mounted in said chamber.
 4. The invention as defined in claim 3 wherein said means for injecting said water spray comprises a nozzle connectable to a supply of water.
 5. The invention as defined in claim 3 wherein said means for injecting said water spray comprises first and second opposed nozzles, each of said nozzles being connectable to a source of water. 